The rapid development of nanotechnology has generated considerable increase in the manufacture and use of engineered nanoparticles (NPs) in a large variety of applications and consumer products. While NPs have enabled unique technological developments, their large-scale use has also led to increased incidence of release in the environment. Studies dealing with the health and safety implications of engineered nanomaterials have raised concerns over the toxicity of the released NPs, as well as their distribution, concentration, fate and transport.
For example, in a recent report released by the Working Party on Manufactured Nanomaterials, CeO2 has been listed as one of the engineered NPs with relevance in the workplace. In the industrial sector, CeO2 NPs are widely used as a polishing abrasive in the chemical mechanical planarization process (CMP) in the manufacturing of printed circuits by the semiconductor industry and as a fuel additive in diesel particulate filters by the automotive industry. Therefore, CeO2 NPs are released and can be found into the environment particularly in heavy traffic and in semiconducting manufacturing areas. According to a Health Effect Institute (HEI) report, emissions of CeO2 were expected to reach a level of 22 million pounds annually in the European Union resulting from CeO2 use as a diesel engine additive. Recent literature regarding the health effects of CeO2 NP exposure indicates that the size, oxidation state, and concentration of CeO2 NPs can influence the various transformations that determine environmental and biological impact, and support the practice of minimizing concentrations in waste and water treatment facilities.
Despite the large presence of NPs, methods enabling their separation, capture and tracking are limited. Functional materials and devices that are able to collect and quantify the concentration and size distribution of NPs in real time can contribute to the development of technology that can address these critical challenges. The ideal NP tracking system is one that is easy to manufacture, inexpensive enough to be used in large scale applications and that can efficiently capture and detect NPs, making it suitable for field measurements. Such measurements are critical for evaluating concentration, distribution and effects of NPs for environmental, clinical, epidemiological and occupational exposure studies.
Traditional methodologies to characterize NPs such as transmission electron microscopy (TEM), scanning electron microscopy (SEM) and atomic force microscopy (AFM) are expensive, time consuming and cannot be used in the field. Several recent works dealing with the development of rapid methods for NP detection proposed the use of organic dyes to identify metal and metal oxide NPs in colloidal dispersions. Determination of size and concentration of Au NPs was also demonstrated by using fast scan cyclic voltammetry with liquid chromatography separation7 and by UV-Vis spectra in conjunction with theoretical simulation. Citrate-stabilized Au and Ag NPs were measured in drinking water using acid-base indicators. Color based detection by monitoring the catalytic activity of NPs using a soluble organic dye, methylene blue, and a reducing agent, sodium borohydride was employed to measure NPs in biological and environmental samples. The method was demonstrated for different types of colloidal NPs and showed color responses to both metallic and metal oxides. Therefore, the method is not specific to the NP characteristics, such as composition, size, concentration, and reactivity. Recently, the single-particle inductively coupled plasma mass spectrometry (ICP-MS) technique received considerable attention as a method to identify and determine the concentration of nanoengineered materials in water samples, including CeO2 NPs. This procedure is very sensitive but requires high cost instrumentation, trained personnel and has limited availability.
Accordingly, there is a continued need in the art for inexpensive and easy-to-use quantitative methods and systems to facilitate rapid capture, assessment, and/or measurement of nanoparticles (NPs).